This invention relates to a double lock trailer coupling of the type in which a latch and the rotatable shaft it is mounted on must be shifted along the longitudinal axis of the shaft in order to open the coupling, and more particularly to a mechanism that facilitates movement of this shaft.
Trailer couplings, of the type where the eye of a draw bar is placed on a cylindrical coupling member and is held in place on the coupling member by a prong that contacts the tip of the coupling member, have a mechanism to rotate either the prong or the coupling member in order to install or remove the draw bar. In order to prevent accidental opening of the trailer coupling, it must have a lock mechanism, and preferably it should have a double lock that requires two distinct actions before the trailer coupling will open. A trailer coupling of this type having a double lock mechanism is disclosed in Weiss U.S. Pat. No. 2,842,380. The Weiss trailer coupling includes a hollow body that is attachable to a vehicle and has a rearwardly projecting prong. A coupling member, that receives the draw bar eye, is rotatably mounted in the body for movement between a closed position where it contacts the prong, and an open position where it is separated from the prong. A latch, that is rotatably mounted in the body, is urged downwardly by a spring into contact with the forward end of the coupling member when the coupling member is closed. Thus, the latch must be rotated away from the coupling member before the coupling member can be opened. The latch is mounted on a shaft which is rotatably mounted in the body and is slidable along its longitudinal axis. A spring normally urges the latch against one side wall of the body, and the latch has a protruding tongue that engages a lug located on the body side wall when the latch is in its normal position to prevent rotation of the latch away from the coupling member. Thus, to open the coupling member, the shaft must first be pulled sideways and then rotated, which is accomplished through a handle mounted on the end of the shaft.
While this mechanism provides an effective double lock, if there is a load on the draw bar it can be transmitted through the coupling member to the latch, making it extremely difficult to pull the latch away from the lug so that it can be rotated. When this occurs it often is necessary to strike the handle with a hammer, which not only is inconvenient but can create uncontrolled opening action.
The subject invention overcomes the foregoing shortcoming of the prior art trailer couplings of this type by placing a cam element on the shaft, which causes the shaft to be moved longitudinally to pull the latch away from the lug when the cam element is rotated. A lever handle associated with the cam element provides a mechanical advantage that assists in its rotation.
In a first embodiment, the cam element is an annular ring that encircles a portion of the shaft that extends out of the body. The ring is joined to the shaft by a pin that extends rotatably through the shaft and is attached at each of its ends to the ring. The ring has a flat side that contacts a flat face on a boss formed in the body when the latch is in its normal longitudinal orientation. The handle is L-shaped, with a shorter portion that is attached to the ring, and has an axis that is normal to the center line of the pin, and a longer portion that is parallel with the shaft and extends over the prong.
In a second embodiment, the ring is joined to the shaft by a stop that is attached to the terminal end of the shaft such that the ring is sandwiched between the stop and the boss.
Accordingly, it is a principal object of the present invention to provide a handle assembly for a trailer coupling that utilizes a rotating cam element to facilitate moving the latch sideways so that it can be rotated away from the coupling member.
It is a further object of the subject invention to provide such a trailer coupling that has a lever handle that provides a mechanical advantage for rotating the cam element.
It is a still further object of the subject invention to provide such a trailer coupling in which the cam element is an annular ring that encircles the latch shaft and engages the body of the trailer coupling when it is rotated.
It is a yet further object of the subject invention to provide such a trailer coupling in which the handle is L-shaped with a shorter portion having an axis that is normal to the latch shaft, and a longer portion having an axis that is parallel with the latch shaft.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.